Closed loop thermodynamic systems utilizing a vaporizable fluid, for the transfer of energy from an energy source to an energy utilizing means or for conversion of energy from thermal energy to mechanical energy, are well known. Such systems are particularly suited for solar energy conversion establishments in remote locations.
Typically, in a closed loop thermodynamic system of the type contemplated in relation to the present invention, a vaporizable working fluid undergoes a change of state from its liquid to its vapor form and back during a complete thermodynamic cycle. The system typically includes a boiler or other comparable element that receives thermal energy from an external energy source (e.g., the sun or a furnace) to vaporize the working fluid from its liquid to its vaporized state, and energy utilizing means (e.g., an engine or radiator) connected to the boiler to receive the vaporized working fluid therefrom at a relatively high specific enthalpy, a condenser or the like that serves as a heat sink and condenses exhausted vaporized working fluid to its liquid state following its productive use in the heat utilizing means and appropriate well known piping and means (e.g., a pump or natural convection) to transfer the condensed working fluid back to the boiler.
As persons skilled in the art must know, in such a closed loop thermodynamic system the Second Law of Thermodynamics requires that at least a portion of the energy received from the external energy source be rejected to a low temperature heat sink for the thermodynamic cycle to repeat itself. Such persons would also appreciate that the newly formed condensate in the condenser is at a relatively low pressure in the system and that cyclical operation of the system requires that the pressure of this liquid working fluid be raised to the working pressure of the boiler.
It is also well known in the thermodynamic arts that thermal regeneration, i.e., a transfer of some of the heat that has to be surrendered by the system to the low temperature heat sink into the condensate prior to its entry into the boiler has the effect of increasing the thermodynamic efficiency of the system. This step of thermal regeneration is most effective, under most practical operating conditions, when the regenerative heat transfer causes energy to be added to the condensate after its pressure has been raised to essentially its highest value.
Closed loop thermodynamic systems, particularly for solar energy conversion establishments, tend to operate at relatively low temperatures and may utilize liquids other than water as the working fluid. Fluids found to be relatively convenient for such uses include freons and ammonia. Obviously, leakage of such a working fluid from the system can be both expensive and undesirable in that it would release a pollutant to the atmosphere Although sealed pumps are known and available, they must always be well sealed to be effective and will require periodic maintenance with consequential interruption in the operation of the overall system. Under such circumstances, it is highly desirable to have a closed loop system in which the working fluid is recirculated by a judicious combination of the force of gravity and the pressure differences available within the system itself.
An example of such a system, titled "Closed Loop Solar Collective System Powering a Self-Starting Uniflow Engine", U.S. Pat. No. 4,698,973 was issued to me on Oct. 13, 1987. It is incorporated herein by reference for its teaching of a non-regenerative closed loop thermodynamic system, the efficiency of which can be improved by the provision of thermal regeneration as disclosed and claimed herein. In this prior art system, the boiler element contains liquid working fluid approximately at a level at which two interconnected and cooperating working fluid holding tanks are located below a condenser element. A uniflow reciprocating vapor driven engine is utilized as an exemplary heat utilizing device in this known system.
There is, however, a need for an improved closed loop recirculation system in which the working fluid is provided with thermal regeneration, in which working fluid holding tanks combine with the rest of the system and a regenerator to utilize the boiler and condenser pressures and the force of gravity to effect recirculation with thermal regeneration in a safe, reliable and efficient manner without the use of a separate pump element to effect the necessary working fluid flows.